1. Field of the Invention
The present invention relates to a method and a system for transferring data and, in particular, to a technique for securely transferring data.
2. Description of the Related Art
A VPN (Virtual Private Network) is a widely used system for securely transferring data through a public network such as the Internet. In a VPN, an encoder is provided on a transmitter side and a decoder is provided on a receiver side, the transmitter side and the receiver side being connected through a public network. Data is encoded (encrypted) at the transmitter side and transmitted through the public network. The receiver side receives the encoded data and decodes the encoded data to restore the original transmitted data. When a VPN is employed, even if the data being transferred over the public network is intercepted, security is maintained unless the encryption is broken.
In the related art, systems for further improving the security from a simple encrypted communication have been proposed. For example, Japanese Patent Laid-Open Publication No. Hei 11-103290 discloses a system in which encoded information is divided into encryption key information and a data portion and the encryption key information and the data portion are transmitted through different routes. Japanese Patent Laid-Open Publication No. 2000-115162 discloses another system in which encoded information is divided into two data portions using an encryption key as a parameter, the data portions are transmitted through different communication routes, and the receiver side synthesizes and decodes the two data portions using the encryption key. Japanese Patent Laid-Open Publication No. 2000-261500 discloses yet another system wherein original data to be transmitted is divided into a plurality of portion units according to pattern data and the divided portions are transmitted through different communication routes.
With a VPN, because VPN ports at the connection between the user network and the public network must remain open, there is a possibility of intrusion via the VPN ports. For this and other reasons, construction of a VPN is normally limited to the interface between networks in which strong confidence exists, such as between a home office and a branch office of the same company, and a VPN for exchange or communication of data cannot be freely constructed between less strongly related parties.
This problem remains with the systems described in Japanese Patent Laid-Open Publication Nos. Hei 11-103290, 2000-115162, and 2000-261500.